Jupiterimages/Thinkstock(NEW YORK) -- The battle against obesity seems to have turned largely into a war on soda.

All across the nation there are calls for taxes on sugar-sweetened drinks and limitations on where they can be sold. The most well-publicized salvo is New York City’s ban on large sugary drinks sold in restaurants, movie theaters and from street carts.

Beverage companies are scrambling to show they’re willing to change their ways to help avoid even more strong-arming. They’re marketing smaller drink sizes and running their own public awareness campaigns for healthy eating.

Their latest preemptive move, announced this week, literally puts the decision to guzzle a sugary drink at a consumer’s fingertips. Soft-drink makers, including Coca-Cola and Pepsico, say they will list the calorie counts for sodas directly on the buttons of their vending machines. The new industry-designed machines go way beyond government proposals, which would only require that calorie counts be displayed on the side of a machine.

Before someone presses 240 -- the number of calories in a 20-ounce Coke -- the machine will scroll a reminder that they can always select a lower-calorie alternative. The machines, which go public in 2013, will also feature small decals with sayings such as “Calories Count: Check Then Choose.”

David Just, the director of Cornell University’s center for behavioral economics in child nutrition programs, said he thinks the machines are a good idea and make a lot more sense than much of the anti-soda legislation. He said he’s worried that moves like the New York City ban will backfire.

“If we do something that specifically targets soda and we don’t know that it will have a huge impact on obesity, we are taking a big risk that it will be ineffective while creating a lot of resentment from consumers and retailers. If we tick off both sides in this transaction, it will be a lot more difficult to introduce new legislation in the future,” said Just.

Just said he thought it makes more sense to get beverage companies to make voluntary changes like the calorie-aware vending machines. He thinks there are other things they can do too.

“Rather than doing a hard sell on sugary drinks to kids and teens, beverage companies could market artificially sweetened and low calorie beverages to them instead,” he said.

Yale University’s Kelly Brownell can be pardoned for not believing beverage company tactics alone will help lower soda consumption and lower obesity rates. Brownell has led the charge to legislate sugar-laden beverages for more than a decade.

“In this country, we start by hoping people will change their behavior on their own. If the default approach of imploring people to change their ways doesn’t work, then we ask the government to step in and take action,” he said.

To Brownell, regulating soda is public health policy 101 -- and it has plenty of precedents. He points to smoking, seat belts and immunization as examples where there was a lot of opposition to regulation at first, but the objections soon receded.